1. Field of the Invention
The present invention relates to electrical terminals and more particularly to a preloaded spring contact terminal of the type received in a connector housing cavity for making electrical contact to a contact member inserted into the housing cavity.
2. Brief Description of the Prior Art
Many preloaded spring contact electrical terminals have been provided in the past for making electrical contact to contact members such as terminal pins, circuit board edge conductor pads and others. Known terminals of this character are typically received within cavities provided in an electrical connector housing. When the contact member is inserted, it engages a contact portion of the terminal. Preloading of a terminal by resilient deformation increases the contact force applied to an inserted contact member.
U.S. Pat. No. 3,697,926 discloses a preloaded spring contact terminal of a type which has been successful in the marketplace. This terminal is received in a connector housing cavity with a base or support portion engaging one cavity wall and with a spaced portion engaging an opposed cavity wall. An intermediate portion acts as a flex spring and is deformed when the terminal is inserted into the cavity in order to provide a preload force with which the spaced portion is biased against the opposed cavity wall. When a contact member is inserted (see FIGS. 7-9) the terminal is further deformed and the spring flex portion applies a contact force to the contact member.
For some purposes, terminals of the type disclosed in U.S. Pat. No. 3,697,926 have disadvantages. One difficulty when small terminals are used in connectors with small center-to-center spacings is that the insertion forces to be overcome when a contact member is inserted are undesirably large and relatively large in comparison with the withdrawal force. Another disadvantage is that a single portion of the terminal functions not only as the contact portion, but also as the abutment portion in engagement with a cavity wall to provide the preload force. This prevents the use of relatively high contact forces because of resulting high insertion forces and unfavorable mechanical advantage as the contact member is inserted. In addition, this configuration results in substantial wiping action at the contact region leading to undesirable wear of the contact portion of the terminal.
United Kingdom Patent No. GB 2079071B discloses an example of a different type of preloaded spring contact terminal. The contact portion of the terminal engageable with an inserted contact member is at a different location than the abutment portion of the terminal engageable with a cavity wall to provide the preload force. The contact portion and the abutment portions are spaced from one another in a direction transverse to the axial direction of contact member insertion. A difficulty with this arrangement is that the terminal is required to be significantly wider than the inserted contact member making close center-to-center spacings difficult to achieve. In addition, a terminal having excessive width is not well adapted to a stamping die progression in which the center-to-center spacing is equal to the center-to-center spacing of cavities of a terminal housing.